1915] 



ATKINSON PHYLOGENY IN THE ASCOMYCETES 



327 



Fig. 5. A and B, Lemanea; C, Batrachosper- 

 mum: cpbr, procarp or carpogonial branch; 

 cpg, carpogonium or egg; tr, trichogyne; sp, 

 spermatium; g, gonimoblast; csp, carpospores. 

 — A and B, after Atkinson; C, after Davis. 



1. The simplest type of cystocarp development occurs in 

 the Nemalionales where the carpogonium, or egg cell, after 

 fertilization, gives rise to several branched sporogenous 

 threads in a compact cluster, bearing terminally the carpo- 

 spores {Nemalion, Lem- 

 anea, etc.), or in some 

 species the sporogenous 

 threads are more widely 

 extended in the thallus, 

 the branches producing 

 separated clusters o f 

 carpospores {Dermo- 

 nema dichotomum, see 

 Schmitz and Haupt- 

 fleisch, '97). Fertiliza- 

 tion by the fusion of a sperm nucleus with the egg nucleus 

 after entrance into the trichogyne and migration down into 

 the carpogonium has been described in Nemalion (Wolfe, '04) 

 and in Batrachospermum (Schmidle, '99; Osterhout, '00). 



2. In Polysiphonia (Rhodomeniales) the procarp branch 

 of four cells is curved around so that the carpogonium is in 

 contact with an auxiliary cell lying between the carpogonium 

 and the pericentral cell which gave rise to the procarp. After 

 fusion of the sperm and egg nucleus in the carpogonium, the 

 fusion nucleus divides once. The carpogonium now connects 

 with the auxiliary cell mentioned, which fuses with the peri- 

 central cell. The two diploid nuclei migrate into the peri- 

 central cell, the carpogonium separates from the auxiliary cell, 

 while it and the remaining cells of the procarp degenerate. The 

 pericentral cell now fuses with several other auxiliary cells, 

 which arose from it as a branch, forming the central cell. The 

 diploid nuclei remain in the upper part of the central cell, 

 while the haploid nuclei from the auxiliary cells, some having 

 divided, now degenerate (Yamanouchi, '06). 



3. A somewhat different situation exists in Erythro- 

 phyllum delesseroides (Gigartinales). The ooblastema fila- 

 ment from the fertilized egg connects with the auxiliary cell 

 which is the basal cell of the seven or eight-celled pro- 



